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dosfsck - doesn't do what you think it should

Wed Nov 27, 2013 1:35 am

I had a corruption on the vfat /dev/mmcblk0p1 partition of my Raspbian SDCard today.

Booted and it dropped into single user mode (asked for root password) with an error on the vfat partition.
So I entered my root password and ran fsck.vfat /dev/mmcblk0p1. Rebooted and the same again.

I pulled the card from the micro SD adapter and because it was the vfat partition tried it in my Win8.1 system. Win8.1 spotted the problem and asked if I wanted to repair it. Did that, then explicitly ejected the card (to ensure everything was written back). Next go in the RPi it booted OK.

So I searched for "dos fsck doesn't fix vfat" on Google and turned up: ... ile-system

The naïve way of running fsck.vfat (or dosfsck (which is just an alias)) didn't automatically repair the filesystem (don't know why). It looks like you need to run it with fsck.vfat -w -r -l -a -v -t /dev/mmcblk0p1 With -w being the most important flag
or it does nothing useful.

I hope that might help some folks who can't get NOOBS or Raspbian to boot.
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Re: dosfsck - doesn't do what you think it should

Wed Nov 27, 2013 7:51 am

If any one else reading is curious about what this criptic command arg's realy mean
Here's a link dosfsck -w -r -l -a -v -t /dev/mmcblk0p1

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Re: dosfsck - doesn't do what you think it should

Wed Nov 27, 2013 8:16 am

From a quick glance at the man page, the important options there appear to be -a and -r
Note: If -a and -r are absent, the filesystem is only checked, but not repaired.
They also appear to be mutually exclusive???
-a Automatically repair the filesystem. No user intervention is necessary. Whenever there is more than one method to solve a problem, the least destructive approach is used.

-r Interactively repair the filesystem. The user is asked for advice whenever there is more than one approach to fix an inconsistency.
The -w option isn't exactly clear. It seems to imply that using it will mean the filesystem is updated during the checking process, rather than at the end.

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Re: dosfsck - doesn't do what you think it should

Tue Jan 28, 2014 7:33 am

Using fsck.fat (dosfstools) from the official raspbian repo will not work. Please read this thread: ... 56#p495156
Using Linux command line usually boils down to these three things:
#1) Respect the privacy of others.
#2) Think before you type.
#3) With great power comes great responsibility.

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